It is known that carboxylic acids can be added to olefins to produce secondary esters (meaning an ester in which the carbon on the alkyl chain to which the carboxylate moiety is attached is a secondary carbon, i.e., one that is covalently bound to two other carbon atoms, rather than a primary or tertiary carbon, which are covalently bound to one or three carbon atoms, respectively). These methods generally involve reaction of a low molecular weight olefin with a high molecular weight carboxylic acid to produce secondary esters.
Catalysts known to be effective in such esterification reactions can be in the form of metallosilicates, especially aluminum silicates (such as zeolites or zeolite mordenites) having exchangeable cations and hydrogen ion-exchanged, layered clays. For esterification reactions, these catalysts are often used with a strong acid added to them.
With hydrogen ion-exchanged, layered clays, it is also known that if the exchangeable cation in the layered clay is a metal cation, there is no need for strong acids to be added to the catalyst. The absence of strong acids renders the clays less corrosive and more readily separable from the reaction mixture.
Stabilized pillared interlayered clay in which the pillars are formed after exchanging the natural cations of the clay with more suitable cations are known to be effective for catalyzing the esterification reaction of olefins and carboxylic acids.
It is also known that monocarboxylic acid methyl esters can be used as the continuous phase or part of the continuous phase in invert drilling muds.
The present invention relates to an esterification reaction of olefins and carboxylic acids which results in a significant decrease in oligomerization and utilizes a catalyst which is relatively easy to prepare and is relatively long-lasting in its effectiveness. The present invention also relates to the product of this esterification reaction which can be used as a component of a drilling fluid.